1. Field of the Invention
This invention relates to method of and system for controlling the restart of an engine, and more particularly to improvements in method of and system for controlling the restart of an engine, suitable for use in an engine for a motor vehicle provided with an electronic air-fuel ratio control device, wherein the fuel amount is increased during restart at high temperature to prevent a restart failure in the engine from occurring.
2. Description of the Prior Art
As one of the methods of feeding an air-fuel mixture of a predetermined air-fuel ratio to combustion chambers of an engine such as a motor vehicle engine, there is one using an electronic air-fuel ratio control device. This method is such that, in an exhaust system in an engine, there is provided an oxygen concentration sensor (hereinafter referred to as an "O.sub.2 sensor") for sensing a rich or lean condition of air-fuel ratio from a residual oxygen concentration in an exhaust gas for example, whereby, for example, a valve opening period of injectors in an electronically controlled fuel injection device (i.e., fuel injection period), or a fuel flowrate or an air flowrate in an electronically controlled carburetor is controlled in accordance with an air-fuel ratio of the exhaust gas sensed by the O.sub.2 sensor, so that an air-fuel mixture of a predetermined air-fuel ratio can be fed to engine combustion chambers, thereby enabling to secure the purification performance of a three-way catalyst provided downstream of the O.sub.2 sensor for reducing HC, CO and NO.sub.X, the harmful contents in the exhaust gas.
In this engine for a motor vehicle provided with the electronic air-fuel ratio control device, when the engine is stopped at high temperature and left as it is, fuel vapor is generated in a fuel line, whereby restart failure may occur. Hence, for example, such a countermeasure has been taken that the fuel injection period may be extended at high temperature in accordance with the temperature of engine cooling water at the time of restart of the engine (e.g., U.S. Pat. No. 3,705,571), or the fuel flowrate may be increased or the air flowrate is decreased, so that the fuel amount can be increased. However, heretofore, no control has been effected on the ignition timing. In consequence, the aspect of the ignition timing control has been rather neglected, and the fuel consumption performance has been sacrificed during idling for example.